U.S. Pat. No. 4,990,134 entitled TRANSLUMINAL MICRODISSECTION DEVICE, issued to David C. Auth on Feb. 5, 1991, describes a rotating mechanical system which is an improvement upon the invention described in U.S. Pat. No. 4,445,509 entitled METHOD AND APPARATUS FOR REMOVAL OF ENCLOSED ABNORMAL DEPOSITS, issued to David C. Auth on May 1, 1984. The aforesaid U.S. Pat. No. 4,990,134 teaches the use of an ellipsoidal cutting head, or burr, which cutting head is coated with tiny diamond chips (shovels). There the cutting head is taught to rotate at a speed which, in conjunction with its geometrical circumference, provides a surface velocity of at least approximately 40 ft/sec. It is also taught in the '134 patent that a tip (burr) of the type described, operating at such a tip velocity, is able to cut soft material at a high removal rate, while generating microscopic particles (on the order of 5 microns or less) and leaving behind a tissue base having a smooth appearance on the surface of the wall of the vessel from which an abnormal deposit has been removed. The result is due to a principle known as "differential cutting," where a moving or rotating blade can differentiate inelastic material from elastic material.
The atherectomy device taught by the '134 patent, known as the ROTABLATOR.RTM. atherectomy device, is marvelously effective at removing plaque. However, this device is not effective to debulk an atherosclerotic arterial lesion to a diameter greater than the diameter of the burr on the drive shaft utilized.
Therefore, there has been a definite need for a rotational ablation device which is capable of debulking the interior of an atherosclerotic artery to a diameter greater than that of the diameter of the burr provided and to do so without unduly adversely impacting upon the interior surface of the wall of the vessel.